The present invention relates to methods for mobile communication control and systems for mobile communication, and particularly to a mobile communication control method and mobile communication system in which mobile IPv6 and SIP (Session Initiation Protocol) are integrated by a core network of 3GPP2 (The 3rd Generation Partnership Project 2).
In the architecture of the third generation cellular network and the 3GPP2 of the International Standard System for the definition of standards, the mobile IPv4 (Internet Protocol version) for supporting the mobility of the terminal is already developed, but IPv6 does not take shape yet. However, the mobile IPv4 has some inherent problems, and thus how the mobile IPv6 is developed by 3GPP2 affords the key to the future mobile wireless data network.
The IP multimedia subsystem IMS has originally been defined by 3GPP, and even 3GPP2 employs the same IMS architecture. The IMS employs SIP (Session Initiation Protocol) for the establishment of session between terminals.
JP-A-2004-120195 discloses a network communication method for the communication of a mobile node (MN) 10 with a communication host (CN) 30 through an IP network as shown in FIG. 12. In this method disclosed in JP-A-2004-120195, an SIP server 40 is provided in the network in order that the communication can be started by using the SIP. The mobile node 10, when connected to a network to which it moved, acquires a Care-of-Address CoA that this network manages, and notifies a home agent server (HA) 20 of the acquired Care-of-Address.
The communication host 30, at the communication start time, transmits a session connection request message (INVITE) to the SIP server 40 before it transmits a data packet (IP packet) to the mobile node 10. The session connection request message is transferred from the SIP server 40 to the home agent server 20, and then it is transferred from the home agent server 20 to the mobile node 10.
The mobile node 10 that received the session connection request message transmits a response message through the SIP server 40 to the communication host 30. When the communication between the communication host 30 and the mobile node 10 is started, the IP data packet that the communication node 30 transmitted is encapsulated in the home agent server 20, and transferred to the mobile node 10 according to the Care-of-Address.
In the communication method proposed in JP-A-2004-120195 all packets transmitted and received between the communication host 30 and the mobile node 10 are transferred through the home agent server 20 of the mobile node 10. Therefore, a triangle routing problem is caused, thus burdening the home agent server and whole network with a heavy communication load.
The SIP and mobile IPv6 both support the mobility of the mobile node MN, but they are different in supporting the mobility. In other words, since the mobile IPv6 is the protocol for IP layer, the TCP layer and the upper layers do not notice that the IP address is changed. Therefore, the application program cannot detect the movement of the mobile node MN. On the other hand, since the SIP is the protocol of the application layer, a re-request message (re-INVITE) can be used to recover the session intermitted as the mobile node MN moves. However, since this kind of standard cannot hide the change of IP address in the TCP layer, the TCP session is intermitted.
Since the mobile IPv6 is transparent to all applications, only the mobile IPv6 in the IMS system can support the normal movement session without the mobility support by the SIP. However, when the mobile node MN moves away from the home area to an external area, and located in that area, all the signaling process for connecting a new SIP session is sure to go through the home network. Therefore, useless routing occurs, thus causing a long delay of time and a heavy traffic load within the home agent HA.
It is an objective of the invention to provide a mobile communication control method and mobile communication system in which the mobile IPv6 and the SIP are integrated in a core network of 3GPP2.
It is another objective of the invention to provide a mobile communication control method and mobile communication system capable of reducing the load of the mobile node on the home agent and mobile communication network.
It is still another objective of the invention to provide a mobile communication control method and mobile communication system that makes it easy to register the position of the mobile node to the SIP server when a new Care-of-Address is acquired, and to connect the session.